The present invention relates to a boiler of a combustion plant comprising at least one heat exchanging device which can be traversed by a medium from an inlet to an outlet and is held in the interior space of the boiler by means of at least one suspension device. Also described is a cleaning control device for a boiler of a combustion plant with at least one heat exchanging device and at least one cleaning unit for removing combustion residues. The invention also relates to a cleaning method for the selective cleaning of at least one heat exchanging device in the boiler of a combustion plant, and to a method for operating a combustion plant. The invention is used in particular in the field of steam generation, of boiler plants heated with fossil fuels and/or additives, refuse combustion plants etc.
The residues from the combustion of coal and/or additive fuels lead, in operation of boilers of a combustion plant, to contamination of the heat exchanging surfaces, which has adverse effects on the operation of the combustion plant. The results are for example efficiency losses as a result of an increased waste gas temperature and/or a required relatively intense cleaning of the heat exchanging surfaces. In addition, the combustion plant must if appropriate be shut down in order to remove stubborn slag accumulations. It is also a problem that, under some circumstances, combustion residues can accumulate in a concentrated fashion at one position of the combustion plant, wherein said so-called “barbs” can possibly detach from the walls and cause damage as they impact against devices of the combustion plant. For these reasons, it is expedient for the combustion residues to be removed from the heat exchanging surfaces at predefined time intervals.
A plurality of different cleaning concepts is already known for cleaning heat exchanging surfaces of said type. For example, in addition to the mechanical cleaning (for example by means of so-called knocking devices or steel balls) and cleaning by means of compressed air or sound, cleaning of the heat exchanging surfaces by means of steam or water is often also resorted to. For cleaning, heat must firstly be extracted from the slag accumulations before they solidify. Cold water is particularly suitable as a cleaning medium for this purpose. The breakdown and detachment of the combustion residues is brought about by means of the sudden evaporation of the impinging and infiltrating water and the associated increase in volume and by means of the kinetic action of the impinging cleaning jet. The thermal shock action which is desired for the combustion residues can however lead to additional stresses in the tube material, which stresses can cause damage with uncontrolled use of the cleaning method. Blowing jet speed, cooling time, blowing jet geometry, water quantity and other factors determine the intensity of the thermal shock.
For cleaning by means of a blowing medium, translatorily movable and stationarily pivotable blowers are known. Movable blowers such as for example sliding blowers, lance blowers, longitudinally movable blowers, rotary tube blowers, rake blowers, are often used only for cleaning purposes in inner regions of the boiler. Said movable blowers are accordingly moved translatorily inwards, with the lance which conducts the cleaning medium if appropriate rotating, so that the nozzles which are attached to the lance clean the environment around the lance. In the case of stationarily pivotably attached blowers, for example, single nozzles, steam cannon blowers or else so-called automatic water lance blowers (manufacturer: Clyde Bergemann GmbH) are installed. In the case of the water lance blowers, the cold water is supplied with a pressure of 12 to 15 bar. The effective length of the blowing jet is approximately 20 to 22 m and the blowing area per blower is 200 to 400 m2, so that a cleaning unit of said type is particularly suitable for cleaning opposite wall regions of the boiler in the case of a free interior space. The blower generates a water jet whose impingement diameter is advantageously less than 1 m, so that a surface can be cleaned by means of targeted, meandering blowing patterns.
The cleaning with water jets briefly influences the combustion process, changes the behavior of various combustion regulating circuits and the steam quantity. The injected cold water also influences the flue gas temperature, the flue gas quantity and the transferred heat quantity. The cleaning of combustion chamber tube walls with water jets also loads the tube material, since the latter is subjected to increased heat stresses as a result of the thermal shock.